Vehicle occupant restraint systems that detect vehicle crash conditions and that actuate vehicle occupant restraining devices are known in the art. Such a vehicle occupant restraint system includes a vehicle crash sensor, such as an inertia switch or an accelerometer, and one or more vehicle occupant restraining devices, such as air bags. The air bags may include a first air bag located forward of the occupant, e.g., in the instrument panel or steering wheel, and a second air bag located in a side door. A vehicle occupant restraint system that includes such front and side mounted air bags also includes a control scheme to control deployment of the air bags in response to a detected crash condition.
U.S. Pat. No. 3,720,426 to Johnson discloses a system for controlling actuation of a plurality of vehicle safety devices including front, rear and side air bags. The '426 system includes a crash sensor/actuation device. The crash sensor/actuation device includes an inverted hollow conical housing containing a free metal ball and a plurality of arcuate electrical contact pairs. Each electrical contact pair is controllably connected to an associated air bag. During vehicle deceleration, the metal ball rolls up the sloped sidewall of the conical housing. Upon the occurrence of a predetermined deceleration of the vehicle, i.e., in a crash condition, the metal ball rolls up the sloped sidewall and makes contact with one of the pairs of electrical contacts, thereby closing an associated electric circuit. The pair of electrical contacts that is contacted by the metal ball is dependent upon the direction of the vehicle crash. The contact of the metal ball with the pair of electrical contacts results in deployment of the associated air bag.
U.S. Pat. No. 5,172,790 to Ishikawa, et al. discloses a vehicle crash discrimination system for controlling actuation of a side mounted air bag during a crash in which an impact is directed against a door at the side of the vehicle. The '790 system includes a plurality of sensors. A control unit monitors the sensors and, upon the occurrence of a crash condition, controls which air bag is to be deployed in response to the outputs of the sensors. The sensors include a deceleration sensor which is mounted on the driver's door. Another deceleration sensor is mounted on the passenger's door. A weight sensor for sensing the "seated" state of a passenger is mounted in the driver's seat, and another such weight sensor is mounted in the passenger's seat. The sensors further include a belt lock sensor for the driver's seat and another belt lock sensor for the front passenger's seat. Each of the belt lock sensors senses whether an occupant of the respective seat is wearing the associated seat belt. The control unit monitors the sensors to control deployment of the air bags in response to outputs of the sensors. When a deceleration signal from one of the door mounted sensors indicates the occurrence a side crash into the associated door, the control unit actuates one or both of the side mounted air bags. Actuation of the air bags is further dependant upon the status of the weight sensors and belt lock sensors.